1. Field of the Invention
The present invention relates to a device for unwinding a flexible support wire for vines.
2. Description of the Related Art
Recent years have seen the development of a cultivation method known as “lateral extension growth,” which is currently being used primarily to grow tomatoes in greenhouses.
In this method, the young plant is attached to the vertical support wire paid out from the dispenser, which is fastened, substantially vertically from said plant, to the carrier cable stretched horizontally near the roof of the greenhouse, that is, generally several meters off the ground. This carrier cable is disposed above a row of plants whose spacing depends on the type of plant concerned.
The plant is guided during its growth by the support wire, and is fastened to it by means of suitable attaching devices as it increases in size.
When the fruit-bearing, aerial portion of the plant attains a height that makes access difficult, a given additional length of support wire is paid out and the dispenser is moved along the carrying cable by translating the rack. The unproductive lower portion of the plant thus forms a curve that droops onto the ground. This operation is repeated several times during the growth of the plant, which may reach lengths of more than dozen meters (for example in the case of tomatoes).
This cultivation method makes it possible to increase the yield of cultivated areas and to save on labor and the purchase of young plants.
The document WO96/29855 describes a device of the aforesaid type, in which one of the side plates of the winding reel is integrally equipped with a ratchet wheel. The dispenser comprises a roughly L-shaped locking lever, with two branches that form an acute angle. The large branch is mounted pivotably on the rack, and comprises, between the pivot point and its free end, a projecting part that is oriented toward the wheel and constitutes a latch that is able to cooperate with the ratchets. The portion of the large branch that lies between the pivot point and the junction area of the projecting part is flexible and elastic. The small branch, for its part, is designed to cooperate by its free end with the carrier cable, which has a suitable cross section.
The free end of the large branch constitutes a region for the application of manual pressure to cause the locking lever to pivot until the free end of the small branch is brought into contact with the upper face of the carrier cable. The pivoting of the locking lever thus is blocked. From this state, if the operator presses harder, the portion of the large branch between the pivot point and the junction area of the projecting part deforms elastically. If enough pressure is applied, the deformation can be such that it causes the ratchet wheel to be released as a result of disengagement of the latch. The weight of the plant then causes the reel and, concomitantly, the ratchet wheel to rotate. The ratchets are in continuous contact with the lower face of the carrier cable. The rotation of the ratchet wheel imposed by the weight of the plant causes the dispenser to undergo a translational movement along the carrier cable in the direction in which the manual pressure was exerted.
Thus, to bring about the release of a support wire, it is necessary to take the rack in one hand without detaching the cable dispenser and to exert pressure on the large branch of the locking lever with the other hand.
A device of this kind, however, has the disadvantage that the user has to climb a ladder or other object and use both hands simultaneously. Thus, neither hand is free to take hold of a guard rail to prevent falls. Keeping in mind that these troublesome manipulations are performed more than 3 m off the ground, it will be appreciated that the work becomes dangerous and very tiresome (due to the necessity of repeatedly climbing the ladder or other object), considering that a greenhouse can require the use of several thousand unwinding devices.